Improved Extraction-Separation of Lanthanum/ Europium Ions by Bis(2-ethylhexyl)phosphoric Acid Using 12-Crown-4 as an Ion Selective Masking Agent

Document Type: Research Article


Department of Chemistry, Faculty of Science, Zanjan University, P. O. Box 45195-313 Zanjan, I.R. IRAN


The extraction-separation of lanthanum and europium ions with bis(2-ethylhexyl) phosphoric acid (DEHPA) in cyclohexane was improved by adding 12-crown-4 (12C4) to the aqueous phase as a masking agent. In the presence of this crown ether the extraction curve of lanthanum ions versus pH shifts to the higher pH region, while the curve is not influenced for the europium ions. Consequently the separation of these ions is enhanced. The treatment of the extraction data in the presence of 12C4 allows to determine the stability constant of the lanthanum-crown ether complex in the aqueous phase. The results have been compared with those reported using 18-crown-6 (18C6). This comparison shows that the improvement in the separation of La/Eu in the presence of 12C4 is the same order as in the presence of 18C6. The influence of temperature on the extraction of the studied cations in the absence and the presence of 12C4 by DEHPA in cyclohexane is studied in the range 293-305 K. This study leads to assess the thermodynamic parameters i.e. the free energy (DGº), enthalpy (DHº) and entropy (DSº) changes associated with the extractionprocess as wellas those of the complexation oflanthanum ions by12C4 in aqueous phase.


Main Subjects

[1] Cotton, F. A.  and  Wilkinson, G. W., “Advanced Inorganic Chemistry”, Interscience Publishers, New York (1985).

[2] Horwitz,  E. P. and  Chiarizia,  R., in “Separation Techniques in Nuclear Waste Management”, Chipmen N. A. C. and Wai M. (Eds), CRC: Florida (1996).

[3] Stary, J., “The Solvent Extraction of Metal Chelates”, Pergamon Press, London (1964).

[4] Motomizu, S. and  Freiser, H., Solvent Extr.Ion Exch., 3, 637 (1985).

[5] Lévéque, A. and Maestro, P., Technique del’Ingenieur J., 6, 630 (1993).

[6] Araki, T., Asai, H., Tanaka, N., Kimata, K., Hosoya, K. and Narita, H., J. Liq. Chromatog., 13, 3689 (1990).

[7] Izatt, R. M., Bradshaw, J. S., Nielsen, S.A., Lamb, J. D. and Christensen, J. J., Chem. Rev., 85, 271 (1985).

[8] Zolotov, Y. A. (Ed), “Macrocyclic Compounds in Analytical Chemistry”, John Wiley, New York (1997).

[9] Hasegawa, Y., Masuda, M., Hirose, K., Solvent Extr. Ion Exch., 5, 255 (1987).

[10] Tsurubou, S., Mizutani, M., Kadota, Y., Yammamoto, T., Umetani, S., Sasaki, T., Le Q. T. H. and Matsui, M., Anal. Chem., 67, 1465 (1995).

[11] Umetani, S., ICR Annual Report, 6, 14 (1999).

[12] Umetani, S., Tsurubo, S., Sasaki, T. and Komatsu, Y., RIKEN Review, 110 (2001).

[13] Zamani, A. A. and Yaftian, M. R., Sep. Purif. Technol., 40, 115 (2004).

[14] See for example: (a) Yaftian, M. R., Burgard, M., Wieser, C., Dieleman, C. B. and Matt, D., Solvent Extr. Ion Exch., 16, 1131 (1998); (b) Yaftian, M. R., Vahedpour, M., Burgard, M. and Matt, D., Iran. J. Chem. Chem. Eng., 19, 60 (2000); (c) Yaftian, M. R. and Vahedpour M., Phosphorus, Sulfur and Silicon 174, 93 (2001).

[15] Yaftian, M. R., Taheri, R., Zamani, A. A. and Matt, D., J. Radioanal. Nucl. Chem., 262, 455 (2004).

[16] Biswas, R. K., Banu, R. A.  and  Islam,  M. N., Hydrometallurgy, 69, 157 (2003).

[17] Fraizier, R. and Wai, C. M., Talanta 39, 211 (1992).